First off, I'm a completionist that for some reason I am compelled to have everything placed.... If I was to nuke, and believe me...that's a huge IF. I would start with my SP. Then, I would most likely place my largest items and estates/mansions. Next, I would rebuild my favorite previous districts, for me it would be my park and cemetery. From there I would mostly do housing and businesses blocks while sprinkling in the odds and ends.
EDIT:
Easier said then done, just break it down to doable tasks using the items you like most.
